EFFICACY OF UV IRRADIATION AS AN ALTERNATIVE NON-THERMAL
PASTEURIZATION METHOD TO PRODUCE MINIMALLY PROCESSED JUICE FROM
CONCORD, NIAGARA AND RIESLING GRAPES
A Project Paper
Presented to the Faculty of the Graduate School
of Cornell University
In Partial Fulfillment of the Requirements for the Degree of
Master of Professional Studies in Agriculture and Life Sciences
Field of Food Science and Technology
by
Vanessa Paola Moncayo Herrera
May 2015
ABSTRACT
The use of UV light as a safe alternative to thermal pasteurization was approved by
FDA in 2000. This study evaluates the efficacy of UV treatment to produce safe grape
juice from three varieties (Concord, Niagara and Riesling) through microbiological
validations and shelf-life studies. Grape juices were inoculated with approximately 107
CFU per mL of E.coli ATCC 25922, a surrogate for E. coli O157:H7, and exposed to a
UV dosage of 14 mJ·cm-2 using CiderSure 3500, a common commercial UV pasteurizer.
Regardless of the grape variety, reductions greater than 5 log10 were achieved. Results
from shelf-life studies showed that UV treated grape juices have a shelf-life of one to
two weeks under refrigerated conditions (7°C).
iii
BIOGRAPHICAL SKETCH
Vanessa Moncayo was born in July 1988 in New Jersey and moved to Quito, Ecuador.
She graduated with a B.S in Food Engineering in 2013 from San Francisco de Quito
University. In 2014, she obtained the “Universities of Excellence Scholarship” provided
by the Ecuadorian government which let her pursue her Master in Professional Studies
(MPS) degree at Cornell University. Under the advice of Dr. Olga Padilla-Zakour,
Vanessa studied the application of UV light as a non-thermal pasteurization treatment
for grape juices. In addition, Vanessa served as a Quality Assurance intern in Cornell
Dairy Plant for two semesters. Through her time at Cornell University Vanessa received
the “2014-2015 Western NY IFT Scholarship” for outstanding achievement in Food
Science graduate studies, as well as the “2014-2015 Goya Foods Prize” for outstanding
graduate student in the field of Food Science & Technology working in the area of fruits
and vegetables. Her interest in product development brought her to lead the 2014-2015
Ocean Spray Product Development team, which took the first place in the competition.
After graduating from Cornell University, Vanessa will return to Ecuador and will work
for the food industry in the area of product development.
v
ACKNOWLEDGMENTS
First, I would like to thank God for his pouring blessings over my life!
Thanks to my dear advisor Dr. Olga Padilla-Zakour for her support, kindness and
guidance as well as her encouragement and care throughout my time in Cornell. I
couldn’t be happier for having an advisor like her. Thanks to John Churey for his
unconditional help, for patiently answering all of my questions and making the lab in
Geneva exciting. To Herbert Cooley and Tom Gibson, thanks for their gentleness and
assistance in the pilot plant. Thanks to Jessie Usaga for her kindness and guidance in
this project. Thanks to Deanna Simmons and Tim Barnard for their daily support and
care and for sharing their Dairy Science knowledge with me. I will miss you so much!
Thanks to my wonderful family for being my pillar and believing in me. Thanks for the
unconditional love, care and prayers all the way from Ecuador.
To my awesome and fun lab mates Michelle Maldonado, Marcela Villareal, Marcela
Patino and Liz Buerman for making the lab such an enjoyable and happy place to be.
Thanks to Charles Lee, Michelle Maldonado and Kent Hsieh for being my family in
Ithaca and for all the unforgettable memories we had together: Michelle thanks for
sharing this experience with me, you have been the best roommate, friend and lab
mate! Kent thanks for making me laugh and for cooking the best Chinese food ever!
Charles, thanks for your love, care, support and for inspiring me to be better!
Thanks to the Ecuadorian Government, SENESCYT (Secretaria de Educacion Superior
Ciencia Tecnologia e Innovacion) for funding my graduate studies.
Finally, thanks to Cornell for making me feel at home during this time, I would never
forget this place and its lovely people!
vi
TABLE OF CONTENTS
ABSTRACT
BIOGRAPHICAL SKETCH .............................................................................................. iii
ACKNOWLEDGMENTS ................................................................................................. v
LIST OF FIGURES ........................................................................................................ viii
LIST OF TABLES .......................................................................................................... viii
INTRODUCTION ............................................................................................................. 1
Importance of Grape Production in United States ....................................................... 1 Juice Processing.......................................................................................................... 2 UV irradiation ............................................................................................................... 3 UV Disinfection System ............................................................................................... 5 CiderSure 3500 ........................................................................................................... 6 Objectives .................................................................................................................... 8 General Objective ........................................................................................................ 8 Specific Objectives ...................................................................................................... 9
MATERIALS AND METHODS ........................................................................................ 9
Grape Juices ............................................................................................................... 9 Physicochemical measurements ............................................................................... 10 UV Treatment ............................................................................................................ 10 Microbiological Validation: UV light treatment ............................................................ 11 Shelf Life Study ......................................................................................................... 12 Statistical Analyses .................................................................................................... 12
RESULTS AND DISCUSSION ...................................................................................... 13
Shelf-life Study .......................................................................................................... 13 Validation Study ......................................................................................................... 18
CONCLUSIONS ............................................................................................................ 21
FUTURE WORK ........................................................................................................... 21
APPENDIX .................................................................................................................... 22
Raw Juice Microbiological Data ................................................................................. 22 Shelf-life Study Data .................................................................................................. 23 Microbiological Validation Data .................................................................................. 26
REFERENCES .............................................................................................................. 28
vii
LIST OF FIGURES
Figure 1. CiderSure 3500 Diagram ............................................................................... 6
Figure 2. Yeast & Mold (PDA) counts of refrigerated UV-processed grape juices ...... 16
Figure 3. Total aerobes (PCA) counts of refrigerated UV-processed grape juices ...... 17
Figure 4. Average log-reductions of E. coli ATCC 25922 achieved in inoculated grape
juices after exposure to UV treatment .......................................................... 20
viii
LIST OF TABLES Table 1. Physico-chemical characterization of grape juices for shelf-life studies .......... 13
Table 2. Microbiological counts of grape juices before and after UV treatment ............. 15
Table 3. Pysico-chemical characterization of grape juices used for microbiological
validation of UV treatment ............................................................................... 18
Table 4. Efficacy of UV treatment reducing E. coli ATCC25922 in inoculated juices ... 19
1
INTRODUCTION
Importance of Grape Production in United States
Grape is a high value fruit crop in the United States. In 2014, there were 1,049,600
acres of grape bearing land in the United States, with New York State accounting for
37,000 acres. The total production of grapes in the United States was 7,769,630 tons,
of which 188,000 tons were produced in the State of New York. The utilized production
of grapes in the country in 2014 was about 7,757,480 tons. Only 13% of the total
utilized production of grapes were destined to fresh consumption, while 87% (6,744,560
tons) were destined for processing. Processed grape utilization has an average value
per ton of $629 which means that in the United States the processed grapes utilization
value was $4,244,132,000 dollars in 2014 (USDA, 2015).
The grape utilization for juice processing increased from 346,950 tons in 2012 to
549,920 in 2014, with an average price of $206 per ton of juice produced.
Concord and Niagara grapes represent an important part of the grapes used for used
processing purposes in the US. Concord grape processed utilization rose by 62%, from
310,140 tons in 2012 to 505,290 tons in 2014, while Niagara grapes processed
utilization experienced a rise of 40% from 50,150 tons in 2012 to 70,370 in 2014
(USDA, 2015).
Concord, Riesling and Niagara grapes are cultivated in the State of New York.
Regarding wine and juice grape production, New York State Department of Agriculture
and Markets reports that the state ranks number three behind California and
Washington State. Grapes used for juice production in New York State accounted for 62
2
percent of the total grapes consumed, being 36 percent destined to wine production and
only 2 percent for fresh market. The four main grape producing zones in New York
State are: Lake Erie area, the Finger Lakes area, the Hudson Valley and the eastern
end of Long Island.
Juice Processing
Pasteurization of juice is fundamental to guarantee consumers’ safety. Due to history
of fruit and vegetable juice foodborne illness outbreaks, FDA has established the Juice
Hazard Analysis & Critical Control Points (HACCP) regulation. The regulation states
that a 5-log pathogen reduction must be accomplished for the microbe identified as the
"pertinent microorganism," which is the most resistant microorganism of public health
significance that is likely to occur in the specific juice (FDA, 2004).
Traditionally juices are processed with the application of a heat treatment as a way to
reduce pathogens and spoilage microorganisms. High temperature short time (HTST)
process is the most common method used for juice pasteurization, being aseptic
processing another common heat treatment used for pasteurization. Thermal treatment
is the most efficient and widely used method for pasteurization used in the juice
industry. However, it also brings along undesirable side effects in the product, mainly
loss of sensory attributes (Ortega-Rivas, 2012).
Consumers’ demand for fresher products with better nutritional properties had increased
in the last years. Customers are looking for authentic taste, safer and healthier
products, and natural fresh foods, as well as “green” foods that can be produced in a
3
more environmentally friendly way with sustainable methods and smaller carbon
footprints (Koutchma, 2009).
These consumers’ demands have incentivized the exploration of non-thermal methods,
such as ultraviolet (UV) irradiation, in order to find balance between microbiological
safety and premium sensory quality of processed foods (Ortega-Rivas, 2012). Special
attention has been given to UV application in fresh fruit juices, since FDA approved in
2000 the use of UV-light as a safe alternative treatment to thermal pasteurization of
these products. (Koutchma, 2008). UV has been well studied and established for
treatment of water, air and surface decontamination, yet for liquid foods is still limited
and further studies need to be completed. Liquid foods such as juices present a variety
of optical, as well as physical properties and varied chemical compositions, factors
which influence UV light transmittance, dose, momentum transfer, and as a
consequence microbial inactivation (Koutchma, 2009). UV irradiation has experienced
a rapid acceptance by the juice industry. It is a convenient choice for producers due to
its low capital investment cost, either as a process or when introducing a continuous
inline UV system, compared to other pasteurization methods (Datta & Tomasula, 2015).
Moreover, UV pasteurization is considered a highly efficient process, as well as low
maintenance and environmental friendly (Ortega-Rivas, 2012).
UV irradiation
Ultraviolet processing for disinfection purposes consist of the application of radiation
from the ultraviolet region. The usual wavelength for UV processing is somewhere from
100 to 400 nm. This range can be divided into UV-A (315 to 400 nm) accountable for
4
tanning in human skin; UV-B (280 to 315 nm) responsible for causing skin burning and
ultimately could lead to skin cancer; UV-C (200 to 280 nm) “germicidal range” that
successfully inactivates bacteria and viruses; and the vacuum UV range (100 to 200
nm) which can be absorbed by most substances and therefore can be conducted
through vacuum. When exposed to UV treatment, DNA molecules absorb UV light
producing crosslinking between pyrimidine nucleoside bases thymine and cytosine in
the DNA strand. Due to the mutated base, establishment of the hydrogen bonds with
the purine bases on the opposite strand is impaired. Consequently, DNA transcription
and replication is blocked, compromising cellular functions and leading to death of the
cells, therefore the germicidal effect. Amount of crosslinking is proportionate to the
amount of UV exposure. A minimal dose of 400 J/m2 is necessary for microbial
inactivation to take place (FDA, 2013).
Irradiation effects on microorganisms are subjected to several factors such as: species,
strain, culture and growth phase. Moreover, the kind and composition of the specific
food to be irradiated has a significant influence on these effects. The use of UV light
with germicidal effects has been applied in three particular areas: air disinfection, liquid
sterilization and inhibition of surface microorganisms. In the food industry specific UV-C
irradiation applications include: disinfection of air and water, disinfection of surfaces of
fresh products such as meat, vegetable, poultry, fish, eggs; and pasteurization of
various liquid foods such as milk, fruit juice or cider (Falguera et al. 2011).
5
UV Disinfection System
An UV system consists of a reaction chamber for UV light treatment in the form of
concentric tubing or other designed tubes, an UV-C lamp, containers for the liquids
(juice), plastic tubing, refrigeration system and pumps. Inside the concentric tube
system there is an UV lamp surrounded by a quartz jacket. The liquid product travels
through the annular part of the tube to achieve the required germicidal effect. Usually,
thin films of liquid product are used in order to increase an effective penetration of UV
light into the product, using the laminar flow of liquids. The use of more than one
concentric tubing system increases the germicidal effect on the product without the
necessity to recirculate it through the system. Turbulent flow of the liquid product
promotes improved penetration of UV light as well, guarantying that the whole product
received the identical UV dose. In order to achieve a Log reduction of pathogens of 5 or
greater, the product should be exposed to a treatment dose of at least 400 J/m2 of UV
radiation (Datta & Tomasula, 2015).
Liquid products that can be treated with UV irradiation include: water, viscous sugar
syrup, fruit or vegetable juices, industrial effluents and others. The type of UV lamp
used for the process determines the type of UV technology, which can be classified as
low pressure and medium pressure. Low pressure lamps have a monochromatic UV
output (limited at 254 nm), while medium pressure lamps have a polychromatic output
(185 to 400 nm). The use of low pressure systems are usually more appropriate for
small, intermittent flow application. Medium-pressure systems represent a better fit for
higher flow rates (Ortega-Rivas, 2012).
6
CiderSure 3500
The CiderSure 3500 is one of the most common commercial UV pasteurizers. This
apparatus passes fluid as a thin film on the UV exposed lamp, resulting in complete
penetration of UV light into the fluid. This reactor has eight lamps (Datta & Tomasula,
2015), and its flow rate is controlled by a computer interface that reads the UV
transmission using UV sensors (Koutchma et. al 2009).
Figure 1. CiderSure 3500 diagram
Validation procedure of new technology, such as UV irradiation includes validation of
microbiological safety. For performing microbiological validation studies, a target
pathogen of concern “pertinent pathogen” must be identified. The pertinent pathogen to
7
be used in the challenge study should be selected based on literature review or
discussion with experts (Koutchma et. al, 2009).
The validation process consists of inoculating fruit juices with high levels of the target
microorganisms and expose juices to the UV treatment. By comparing the microbial
population before and after the treatment the log reduction can be calculated and
therefore the effectiveness of UV as a pasteurizing method can be determined (FDA,
2013)
Several studies have been done to validate UV treatment using CiderSure 3500 with
turbulent flow as a 5-log reduction method to pasteurize apple cider. Basaran et. al
(2004) used the CiderSure 3500 to examine the effect of eight different apple cultivars
upon UV inactivation of three strains of E. coli O157:H7. Strains used for this study
were ATCC 43889, ATCC 43895 and 933. The study found that all varieties of apple
juice reached a Log-reduction higher than 5. Another study evaluated the efficacy of
UV irradiation on the inactivation of Cryptosporidium parvum oocysts in fresh apple
cider using a CiderSure 3500A apparatus. Results found a greater reduction than 5-log
obtained by exposing contaminated apple cider to 14.32 mJ/cm2 for 1.2 to 1.9 seconds
(Hanes et. al, 2002). Furthermore, Dong et. al (2010) studied the reduction of patulin
mycotoxin in fresh apple cider by treating it with UV irradiation, with the CiderSure 3500
apparatus. Results showed that an UV exposure of 14.2 to 99.4 mJ.cm2 significantly
reduced the levels of patulin. Patulin levels decreased by 9.4 to 43.4% (depending on
the range of UV dose) after less than 15 s of UV exposure. Quintero-Ramos et. al
(2004) examined the effects of UV light dose (1800 to 20331 µJ/cm2) on the inactivation
of E. coli ATCC 25922 on apple cider. Results found that doses of 6500 µJ/cm2 or
8
higher resulted in the achievement of a greater than 5-log reduction of E. coli. Usaga
et. al (2014) performed validation studies of CiderSure 3500’s quartz tubes by treating
apple cider inoculated with Escherichia coli ATCC25922. An average of 7.0 ± 0.7 log
reductions of E. coli were obtained, being 5.01 log reduction the minimum value
achieved.
Furthermore, Matak et. al (2005) used CiderSure 3500 to study the effects of UV
exposure on the inactivation of Listeria monocytogenes on fresh goat milk. Results
showed that a greater than 5-log reduction can be achieved when milk received a
cumulative UV dose of 15.8 ±1.6 mJ/ cm2
Objectives
Several studies have been conducted to evaluate the efficacy of CiderSure 3500. Most
of these studies have proven the ability of CiderSure 3500 to obtain a log-reduction of at
least 5-log of pertinent pathogens in apple cider. Furthermore, these studies have
focused mainly on the validation of the process and the quality of treated apple cider.
Very limited information can be found regarding the application of UV treatment using
CiderSure 3500 in other juices than apple cider. Additionally, not many studies have
focused in the evaluation of UV treated juices’ shelf-life.
General Objective
The objective of this study is to apply UV irradiation technology using the CiderSure
3500 to produce non-thermal, minimally processed, high quality grape juices from
Concord, Niagara and Riesling varieties.
9
Specific Objectives
To perform the shelf-life study of UV treated grape juices from Concord, Niagara
and Riesling varieties under refrigerated conditions.
To execute microbiological validation of UV light treatment using grape juices
inoculated with E. coli ATCC 25922 at 107 CFU/mL.
MATERIALS AND METHODS
Grape Juices
Three different varieties of grapes: Niagara, Riesling and Concord were used for this
study. All grapes were obtained from a grape yard located in Geneva, NY. Niagara and
Riesling grapes were stored at 0°C and thawed at 7°C for a period of seven days before
processing. Concord grapes were harvested and kept in refrigeration at 7°C for 7 days
before processing. Previous trial using frozen Concord grapes resulted in a purple
colored juice that was not able to be UV treated. Grapes were cold pressed on a
custom made hydraulic press rack and frame, pressing process was performed in 10 kg
batches.
Riesling juice was 17.8° Brix and had a pH value of 3.47. Niagara juice was 16.2 °Brix
and had a pH value of 3.47. Concord juice was 13.7 °Brix and had a pH value of 3.25.
Juice samples were packed into 125 mL (4 oz) Nalgene™ PET Sterile Square Media
Bottles with HDPE Closure (Thermo Scientific, Lima, Ohio).
10
Physicochemical measurements
Grape juice samples were subjected to chemical and physical measurements in
triplicate. pH, titratable acidity (TA), soluble solids (°Brix), turbidity, absorption
coefficient and color (L, a, b) were measured. Accument Basic AB15 pH meter (Fisher
Scientific, Hampton, New Hampshire) was used to measure pH values. TA was
measured by the use of G20 Compact Titrator from Mettler Toledo. Five mL of juice
were sampled and diluted in 35 mL of distilled water. Results were reported as malic
acid percentage (w/v). An Auto ABBE Refractometer Leica 10504 (Leica Inc., Buffalo,
NY) was used to determine total soluble solids of juice, results were reported as °Brix.
Turbidity was measured using a Hach 2100P turbidimeter 4500-00 (Hach Co.,
Loveland, CO) and results were expressed as Nephelometric Turbidity Units (NTU).
Color measurement was performed in a Hunter UltraScan VIS spectrophotometer
(Hunter Lab Assoc., Reston, VA) and results were reported as L, a and b values.
Absorption coefficient (α) was calculated by following the protocol described by
Koutchma et al. (2004). Juice absorption was measured at 254 nm using a UV-1800
spectrophotometer (Shimadzu Scientific Instruments, Columbia, MD). Samples were
subjected to a 10-fold dilution in distilled water and positioned into demountable fused
quartz cuvettes of 0.1, 0.2, 0.5 and 1.0 mm path length (NSG Precision Cells, INC.,
Farmingdale, NY).
UV Treatment
Grape juices UV treatments were performed in the Cider Sure model 3500 UV juice
processing machine (FPE Inc., Rochester, NY) at a wavelength of 254 nm. This
11
machine adjusts the flow rate of the juice and provides a UV dosage of 14 mJ·cm-2.
After UV treatment, juice was manually packed in 125 mL (4 oz) PET Sterile Bottles and
stored at 7°C in a refrigeration chamber. Three samples of each juice were taken every
week for conducting microbiological testing (total plate count, mold & yeast) for the shelf
life study.
Microbiological Validation: UV light treatment
With a sterile loop a single colony of E. coli ATCC 25922 was picked from a petri dish
and inoculated into a culture tube containing 5 ml of TSB (Tryptic soy broth). The
culture was incubated for 5-6 hours at 35-37 °C and 200-250 rpm. One mL of the
culture was transferred into a 500 ml Erlenmeyer flask containing 100 mL of sterile
tryptic soy broth and was incubated for 16-18 hours at 35-37 ºC and 200-250rpm.
Samples of approximately 1.8 L of every variety of grapes were inoculated with 20 ml of
the E. coli ATCC 25922 solution, which is equivalent to an initial population of 107
CFU·ml-1. Juices were sampled and tested previous and after UV processing. Samples
were plated in duplicate, seven serial dilutions in 9 ml of sterile 0.1% peptone water
were made. One mL of each dilution was plated in the petri dishes and later pour-
plated with Trypticase soy agar and taken to incubation for 20 ± 2 h at 35 ± 2 °C. The
log reduction of E. coli ATCC25922 was calculated and reported as the difference
between the log-transformed counts before and after the exposure to UV treatment.
12
Shelf Life Study
Microbiological tests: total plate count, and molds and yeast count were performed
every seven days. Plating with plate count Agar (PCA), Difco, Becton Dickinson
(Sparks, MD) was performed to determine total aerobic microbes population. Plating
with acidified (3.5 pH) Potato Dextrose Agar (PDA), Difco, Becton Dickinson (Sparks,
MD) was performed to determine yeast and mold population. Three bottles of each
juice and treatment were taken for microbiological analysis. One mL of juice sample
was subjected to serial dilutions in 1% sterile peptone water and placed into Petri
dishes. Agar was poured and mixed thoroughly, a duplicate of each dilution was made.
Petri dishes were incubated for a period of 48 h at a temperature of 30°C. Results were
reported as log10 CFU/mL.
Statistical Analyses
Log-reductions among grape varieties were statistically analyzed by analysis of
variance. Statistical significance of difference between sample means were made using
Tukey’s HSD (honestly significant difference) test at significance levels of α=0.05 using
JMP Pro 10, SAS software.
13
RESULTS AND DISCUSSION
Shelf-life Study
Concord juice had a light brown color, pH of 3.26 and soluble solids content of
13.69°Brix. Niagara and Riesling juices had higher pH of 3.47. Niagara and Riesling
juices had a light amber color, soluble solids content of 16.17 and 17.81°Brix. Concord
was the juice with higher turbidity with a value of 607 NTU. Values of absorption
coefficient and acidity were not significantly different among the varieties (α≤ 0.05).
Table 1. Physico-chemical characterization of grapes juices used for shelf-life studies
under refrigerated conditions (7°C)
Grape Variety
pH Soluble Solids (°Brix)
Titratable Acidity (% w/v malic acid)
Turbidity(NTU)
Color Components
Absorption Coefficient (mm-1)
L a b
Concord
3.26 ± 0.06 b
13.7 ± 0.60 b
0.64 ± 0.27 a
607 ± 75 a
28.13 ± 0.30 b
-0.03 ± 0.01 c
0.15 ± 0.07 c
0.175 ± 0.002 a
Niagara
3.47 ± 0.07 a
16.2 ± 1.2 a
0.370 ± 0.004 a
428 ± 18 b
28.44 ± 0.25 b
1.32 ± 0.02 b
2.44 ± 0.26 b
0.152 ± 0.012 a
Riesling
3.47 ± 0.01 a
17.81 ± 0.08 a
0.44 ± 0.04 a
330.33 ± 27 b
29.64 ± 0.21 a
1.44 ± 0.09 a
4.78 ± 0.28 a
0.158 ± 0.010 a
Means ± SD of 3 analytical replicates. Same letters indicate no significant difference at
95% confidence level.
14
Microbiological quality of raw juice was similar between Niagara and Riesling varieties
(α≤ 0.05) with total aerobes counts (PCA) of 55000 CFU/mL (4.73 log10) and 56500
CFU/mL (4.74 log10), and mold & yeast counts (PDA) of 20000 (4.16 log10) and 13033
CFU/mL (4.05 log10) respectively. Concord juice had poorer microbiological quality with
total aerobes counts (PCA) of 247000 CFU/mL (5.38 log10) and mold & yeast counts
(PDA) of 297160 CFU/mL (5.45 log10). UV irradiation decreased raw grape juice total
aerobe counts by 1.53 log10 for Concord, 1.22 log10 for Niagara and 1.25 log10 for
Riesling. Mold and yeast counts were reduced by 1.33 log10 for Concord, 0.65 log10 for
Niagara and 2.24 log10 for Riesling. Tandon et. al (2003)achieved higher reductions
(1.9 for total aerobes and 1.6 log10 for yeast & mold) when treating raw apple cider of
better microbiological quality.
Concord grape juice showed a shelf-life of 1 week under refrigerated conditions (7°C)
while Niagara and Riesling juices showed a shelf-life of 2 weeks under the same
conditions. Similar results of 1-2 weeks of shelf-life were reported by Tandon and
coworkers for UV treated apple cider (Tandon et. al, 2003).
For the three varieties of juice the end of shelf-life was determined by the appearance of
visual mold inside the bottles. These results correlate with previous studies done by
Choi who observed end of shelf-life in apple cider by mold and yeast spoilage (Choi &
Nielsen, 2005).
15
Table 2. Microbial counts of grape juices from Concord, Niagara and Riesling varieties
before and after UV treatment with CiderSure 3500 UV juice processing machine.
Variety
Raw Juice Counts before UV treatment
(log10 CFU/mL)
Juice Counts after UV treatment (log10 CFU/mL)
Shelf-life
Total plate counts
Mold & yeast
Total plate counts Mold & yeast
Concord 5.38 5.45 3.85 4.12 7 days*
Niagara 4.73 4.16 3.51 3.51 15
days*
Riesling 4.74 4.05 3.49 2.69 15
days*
*end of shelf-life was determined by presence of visual mold.
16
Figure 2. PDA plate counts during refrigerated storage (7°C) of UV processed grape juice packed in sterile PET bottles. * indicates end of shelf-life due to presence of visual mold inside the bottle.
17
Figure 3. PCA plate counts during refrigerated storage (7°C) of UV processed grape juices packed in sterile PET bottles. * indicates end of shelf-life due to presence of visual mold inside the bottle.
18
Validation Study
Concord juices used for shelf-life and validation studies were from the same production
batch. Juices from Niagara and Riesling varieties used for the validation study were
different from those used for shelf-life study, therefore their physico-chemical
characteristics are different.
Concord juice had a pH of 3.26 and a soluble solid content of 13.69°Brix. Niagara juice
had a 3.23 pH and 13.45°Brix soluble solids. Riesling juice had a pH value of 3.01 and
17.78°Brix soluble solids. The highest turbidity observed was from Concord at 607
NTU. Acidity was the only physical-chemical characteristic that was not significantly
different among all the grapes varieties (α≤ 0.05).
Table 3. Physico-chemical characterization of grapes juices used for validation of UV
treatment with CiderSure 3500 UV juice processing machine for E. coli ATCC 25922
Grape Variety
pH Soluble Solids (°Brix)
Titratable Acidity (%w/v malic acid)
Turbidity (NTU)
Color Components Absorption Coefficient (mm-1)
L a b
Concord
3.26 ± 0.06 a
13.69 ± 0.60 b
0.64 ± 0.27 a
607 ± 75 a
28.13 ± 0.30 c
-0.03 ± 0.01 c
0.15 ± 0.07 a
0.175 ± 0.002 a
Niagara
3.23 ± 0.04 a
13.45 ± 0.22 b
0.640 ± 0.004 a
156 ± 11 b
32.38 ± 0.56 b
2.67 ± 0.27 a
18.02 ± 1.02 b
0.099 ± 0.002 c
Riesling
3.01 ± 0.04 b
17.78 ± 0.19 a
0.67 ± 0.21 a
185 ± 12 b
33.84 ± 0.54 a
1.37 ± 0.40 b
18.78 ± 1.00 b
0.140 ± 0.004 b
Means ± SD of 3 analytical replicates. Same letters indicate no significant difference at 95% confidence level.
19
UV treatment significantly reduced E.coli ATCC 25922 in grape juices from Concord,
Niagara and Riesling varieties (α≤ 0.05), the average log reduction observed was
6.44±0.36. Log reduction was significantly different between the three varieties. The
lowest achieved reduction was 6.07 log10 obtained for Concord grape juice (Figure 3).
Table 4. Efficacy of UV treatment at 14 mJ·cm-2 reducing E. coli ATCC 25922 in
inoculated grapes juices from Concord, Niagara and Riesling varieties
Juice Variety Population Before UV exposure
log10 (CFU/mL) Population After UV exposure
log10 (CFU/mL)
Concord 7.72 1.64
Riesling 7.36 0.89
Niagara 7.62 0.83
20
Figure 4. Average log10 reductions of E. coli ATCC 25922 achieved in inoculated grape
juices of Concord, Niagara and Riesling varieties after exposure to UV treatment at 14
mJ·cm-2. Same letters indicate no significant difference at 95% confidence level.
Regardless the variety of grape, a reduction greater than 5 log10 was achieved for the
studied juices. These results correlate with previous studies done by Basaran et. al
(2004) and Usaga et. al (2014) where log reductions higher than 5 were achieved when
treating apple cider with UV irradiation, under turbulent flow, at a dosage of 14 mJ·cm-2.
21
CONCLUSIONS Application of UV irradiation with CiderSure 3500 at 14 mJ·cm-2 under turbulent flow on
grape juices from Concord (cold pressed), Niagara and Riesling varieties achieved a
reduction of at least 5-log of E. coli ATCC 25922, representing an effective alternative to
thermal pasteurization treatment. UV irradiation produced quality grape juices with a
shelf-life between 7 and 15 days under refrigerated conditions (7°C). The end of shelf-
life for all the grape juices was determined by the presence of visual mold.
FUTURE WORK
Further studies should be done regarding the effects of UV treatment application with
CiderSure 3500 in grape juices. Different strains of Escherichia coli should be used for
the microbiological validation in order to determine which strain is more resistant to the
process. Moreover, more varieties of grapes could be evaluated to determine how the
physical-chemical properties of grape varieties affect the efficiency of the treatment.
Quality of UV treated grape juice could be evaluated by analyzing chemical and sensory
changes in the UV treated refrigerated samples through the shelf-life time.
Finally, the effect of the combination of UV treatment with other non-thermal treatments
should be studied in order to develop a process that allows the production of high
quality grape juice with longer shelf-life.
22
APPENDIX
Raw Juice Microbiological Data
CONCORD
Total Aerobes Count (PCA)
Rep Dilution Count
1 Count
2 Average Log Total 1 3 196 133 164.5 2.2162 5.22 2 3 348 280 314 2.4969 5.5 3 3 255 272 263.5 2.4208 5.42
Yeast & Mold Count (PDA)
Rep Dilution Count
1 Count
2 Average Log Total 1 3 174 179 176.5 2.2467 5.25 2 3 400 424 412 2.6149 5.61 3 3 346 260 303 2.4814 5.48
NIAGARA
Total Aerobes Count (PCA)
Rep Dilution Count
1 Count
2 Average Log Total 1 3 65 49 57 1.7559 4.76 2 3 73 71 72 1.8573 4.86 3 3 38 36 37 1.5682 4.57
Yeast & Mold Count (PDA)
Rep Dilution Count
1 Count
2 Average Log Total 1 3 20 22 21 1.3222 4.32 2 3 43 27 35 1.5441 4.54 3 3 4 4 4 0.6021 3.6
23
RIESLING Total Aerobes Count (PCA)
Rep Dilution Count
1 Count
2 Average Log Total 1 3 33 48 40.5 1.6075 4.61 2 3 66 83 74.5 1.8722 4.87 3 3 55 54 54.5 1.7364 4.74
Yeast & Mold Count (PDA)
Rep Dilution Count
1 Count
2 Average Log Total 1 2 136 38 87 1.9395 3.94 2 3 9 38 23.5 1.3711 4.37 3 2 18 120 69 1.8388 3.84
Shelf-life Study Data
CONCORD
Total Aerobes Count (PCA)
Day Rep Dilution Count
1 Count
2 Average Log Total
1 1 1 722 784 753 2.87 3.88 2 1 684 710 697 2.84 3.84 3 1 672 704 688 2.84 3.84
7 1 3 3 4 3.5 0.54 3.54 2 3 9 8 8.5 0.93 3.93 3 3 3 12 7.5 0.88 3.87
24
Yeast & Mold Count (PDA)
Daye Rep Dilution Count
1 Count
2 Average Log Total
1 1 1 1240 1216 1228 3.09 4.09 2 1 1408 1460 1434 3.16 4.15 3 1 1268 1324 1296 3.11 4.11
7 1 2 60 53 56.5 1.75 3.75 2 2 154 147 150.5 2.18 4.18 3 2 83 82 82.5 1.92 3.92
NIAGARA Total Aerobes Count (PCA)
Day Rep Dilution Count
1 Count
2 Average Log Total
1 1 2 29 22 25.5 1.41 3.41
2 2 35 25 30 1.47 3.48 3 2 49 42 45.5 1.66 3.66
7 1 4 2 3 2.5 0.39 4.39
2 4 14 18 16 1.20 5.20 3 4 11 26 18.5 1.27 5.27
14 1 2 86 70 78 1.89 3.89
2 2 15 5 10 1.00 3.00 3 3 3 3 3 0.48 3.48
Yeast & Mold Count (PDA)
Day Rep Dilution Count
1 Count
2 Average Log Total
1 1 2 27 22 24.5 1.39 3.39 2 2 14 11 12.5 1.09 3.091 3 2 122 108 115 2.06 4.06
7 1 4 2 2 2 0.30 4.30 2 4 1 1 1 0.00 4.00 3 4 1 1 1 0.00 4
14 1 2 34 29 31.5 1.49 3.49 2 2 6 16 11 1.04 3.04 3 2 10 17 13.5 1.13 3.13
25
RIESLING Total Aerobes Count (PCA)
Day Rep Dilution Count
1 Count
2 Average Log Total
1 1 1 222 91 156.5 2.19 3.19 2 1 334 392 363 2.56 3.56 3 1 603 462 532.5 2.73 3.73
7 1 4 1 1 1 0.00 4.00 2 4 10 10 10 1.00 5.00 3 4 5 8 6.5 0.816 4.81
14 1 2 16 19 17.5 1.245 3.24 2 2 12 13 12.5 1.09 3.09 3 2 46 35 40.5 1.61 3.61
Yeast & Mold Count (PDA)
Day Rep Dilution Count
1 Count
2 Average Log Total
1 1 1 9 11 10 1 2 2 1 88 12 50 1.69 2.69 3 2 10 17 13.5 1.13 3.13
7 1 3 4 3 3.5 0.54 3.54 2 3 1 1 1 0.00 3.00 3 3 1 1 1 0.00 3.00
14 1 2 8 15 11.5 1.06 3.06 2 2 34 20 27 1.43 3.43 3 2 9 1 5 0.69 2.69
26
Microbiological Validation Data
Concord juice inoculated with E. coli ATCC 25922
before UV treatment
Rep Dilution Count
1 Count
2 Average Log Total 1 6 56 56 56 1.75 7.75 2 6 49 54 51.5 1.71 7.71 3 6 50 48 49 1.69 7.69
After UV treatment
Rep Dilution Count
1 Count
2 Average Log Total 1 0 39 36 37.5 1.57 1.57 2 0 37 69 53 1.72 1.72 3 0 33 51 42 1.62 1.62
Niagara juice inoculated with E.coli ATCC 25922
Before UV treatment
Rep Dilution Count
1 Count
2 Average Log Total 1 6 51 35 43 1.63 7.63 2 6 34 41 37.5 1.57 7.57 3 6 47 42 44.5 1.65 7.65
After UV treatment
Rep Dilution Count
1 Count
2 Average Log Total 1 0 11 14 12.5 1.09 1.09 2 0 4 5 4.5 0.65 0.65 3 0 7 4 5.5 0.74 0.74
27
Riesling juice inoculated with E.coli ATCC 25922
Before UV treatment
Rep Dilution Count
1 Count
2 Average Log Total 1 6 30 26 28 1.45 7.45 2 6 22 23 22.5 1.35 7.35 3 6 20 18 19 1.28 7.28
After UV treatment
Rep Dilution Count
1 Count
2 Average Log Total 1 0 6 3 4.5 0.65 0.65 2 0 8 12 10 1.00 1.00 3 0 11 10 10.5 1.02 1.02
28
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